Analysis of the Sponge [Porifera] Gene Repertoire: Implications for the Evolution of the Metazoan Body Plan

Abstract

Abstract. Sponges [phylum Porifera] form the basis of the metazoan kingdom and represent the evolutionary earliest phylum still extant. Hence, as living fossils, they are the taxon closest related to the hypothetical ancestor of all Metazoa, the Urmetazoa. Until recently, it was still unclear whether sponges are provided with a defined body plan. Only after the cloning, expression and functional studies of characteristic metazoan genes, could it be demonstrated that these animals comprise the structural elements which allow the sponge cells to organize themselves according to a body plan. Adhesion molecules involved in cell-cell and cell-matrix interactions have been identified. Among the cell-cell adhesion molecules the aggregation factor (AF) is the prominent particle. It is composed of a core protein that is associated with the adhesion molecules, a 36 kDa as well as a 86 kDa polypeptide. A galee tin functions as a linker of the AF to the cell-membrane-associated receptor, the aggregation receptor (AR). The most important extracellular matrix molecules are collagen-and fibronectin-like molecules. These proteins interact with the cellmembrane receptors, the integrins. In addition, a neuronal receptor has been identified, which -together with the identified neuroactive molecules -indicate the existence of a primordial neuronal network already in Porifera. The primmorph system, aggregated cells that retain the capacity to proliferate and differentiate, has been used to demonstrate that a homeobox-containing gene, Iroquois, is expressed during canal formation in primmorphs. The formation of a body plan in sponges is supported by skeletal elements, the spicules, which are composed in Demospongiae as well as in Hexactinellida of amorphous, noncrystalline silica. In Demospongiae the spicule formation is under enzymic control of silicatein. Already at least one morphogen has been identified in sponges, myotrophin, which is likely to be involved in the axis formation. Taken together, these elements support the recent conclusions that sponges are not merely non organized cell aggregates, but already complex animals provided with a defined body plan.

Phylogenetic diversity of culturable fungi associated with two marine sponges: Haliclona simulans and Gelliodes carnosa, collected from the Hainan Island coastal waters of the South China Sea

“…Marine sponges (Porifera) represent the very basis of metazoan evolution and can be regarded as the oldest animal phylum still alive (Müller and Müller 2003). So far about 15,000 species have been described, but the actual diversity is probably higher (Hooper and van Soest 2002;Fieseler et al 2004).…”

Molecular cloning of partial 14-3-3 genes in the marine sponge Hymeniacidon perleve and its role in differentiating infectious and non-infectious bacteria

“…As sessile filter feeders, sponges (phylum Porifera) are exposed to a large amount of microorganisms, including pathogenic bacteria. Besides their ability to remove microorganisms through phagocytosis [34] and characteristics to produce chemicals with anti-bacterial activity [13], sponges possess an efficient system of immune/defense mechanism [43]. In nearly a decade, the demosponge S. domuncula was used as the model system to study the molecular responses to bacteria [18][19][20][21] and fungi [17].…”

RGD-dependent mechanisms in the endoneurial phagocyte response and axonal regeneration in the nervous system of the snail Lymnaea stagnalis

“…Thus it is conceivable that matricryptic RGD-epitopes that normally do not interact with RGD-selective integrins are involved in the activation of phagocytic cell types during inflammatory-or injury-induced events in the mammalian PNS. Although we have no detailed information about the variety and distribution of ECM proteins expressed in the Lymnaea nervous system the major ECM glycoproteins, including collagens, appeared early in the evolution of metazoans and appear broadly represented in all modern metazoan phyla including gastropod molluscs (Exposito et al, 2002;Garrone, 1998;Miller and Hadley, 1991;Moroz et al, 2006;Müller and Müller, 2003;Serpentini et al, 2000). Hence, future efforts to reveal the identity of the endogenous integrin ligand(s) involved in RGD-dependent injury-induced regulation of endoneurial phagocyte activity should, in addition to fibronectin, also consider proteins containing matricryptic RGD-containing epitopes as possible ligands of interest.…”